chore(consensus): EIP-2718 Encoding Trait Impls (#300)

### Description

Moves custom EIP-2718 encoding and decoding methods on `TxDeposit` into
trait impls for the alloy eip traits.

crates/consensus/src/hardforks/ecotone.rs

@@ -3,6 +3,7 @@
 //! [Transaction]: alloy_consensus::Transaction
 
 use alloc::{string::String, vec::Vec};
+use alloy_eips::eip2718::Encodable2718;
 use alloy_primitives::{address, hex, Address, Bytes, TxKind, B256, U256};
 
 use crate::{Hardfork, TxDeposit, UpgradeDepositSource};
@@ -160,7 +161,7 @@ impl Hardfork for Ecotone {
     fn txs(&self) -> impl Iterator<Item = Bytes> + '_ {
         Self::deposits().map(|tx| {
             let mut encoded = Vec::new();
-            tx.eip2718_encode(&mut encoded);
+            tx.encode_2718(&mut encoded);
             Bytes::from(encoded)
         })
     }

crates/consensus/src/hardforks/fjord.rs

@@ -3,6 +3,7 @@
 //! [Transaction]: alloy_consensus::Transaction
 
 use alloc::{string::String, vec::Vec};
+use alloy_eips::eip2718::Encodable2718;
 use alloy_primitives::{address, hex, Address, Bytes, TxKind, B256, U256};
 
 use crate::{Hardfork, TxDeposit, UpgradeDepositSource};
@@ -98,7 +99,7 @@ impl Hardfork for Fjord {
     fn txs(&self) -> impl Iterator<Item = Bytes> + '_ {
         Self::deposits().map(|tx| {
             let mut encoded = Vec::new();
-            tx.eip2718_encode(&mut encoded);
+            tx.encode_2718(&mut encoded);
             Bytes::from(encoded)
         })
     }

crates/consensus/src/transaction/deposit.rs

@@ -4,7 +4,10 @@ use super::OpTxType;
 use crate::DepositTransaction;
 use alloc::vec::Vec;
 use alloy_consensus::{Sealable, Transaction};
-use alloy_eips::eip2930::AccessList;
+use alloy_eips::{
+    eip2718::{Decodable2718, Eip2718Error, Eip2718Result, Encodable2718},
+    eip2930::AccessList,
+};
 use alloy_primitives::{
     keccak256, Address, Bytes, ChainId, PrimitiveSignature as Signature, TxHash, TxKind, B256, U256,
 };
@@ -192,13 +195,6 @@ impl TxDeposit {
         self.rlp_encoded_length() + 1
     }
 
-    /// EIP-2718 encode the transaction with the given signature and the default
-    /// type flag.
-    pub fn eip2718_encode(&self, out: &mut dyn BufMut) {
-        out.put_u8(self.tx_type() as u8);
-        self.rlp_encode(out);
-    }
-
     fn network_header(&self) -> Header {
         Header { list: false, payload_length: self.eip2718_encoded_length() }
     }
@@ -212,13 +208,13 @@ impl TxDeposit {
     /// Network encode the transaction with the given signature.
     pub fn network_encode(&self, out: &mut dyn BufMut) {
         self.network_header().encode(out);
-        self.eip2718_encode(out);
+        self.encode_2718(out);
     }
 
     /// Calculate the transaction hash.
     pub fn tx_hash(&self) -> TxHash {
         let mut buf = Vec::with_capacity(self.eip2718_encoded_length());
-        self.eip2718_encode(&mut buf);
+        self.encode_2718(&mut buf);
         keccak256(&buf)
     }
 
@@ -299,6 +295,37 @@ impl Transaction for TxDeposit {
     }
 }
 
+impl Encodable2718 for TxDeposit {
+    fn type_flag(&self) -> Option<u8> {
+        Some(OpTxType::Deposit as u8)
+    }
+
+    fn encode_2718_len(&self) -> usize {
+        self.eip2718_encoded_length()
+    }
+
+    fn encode_2718(&self, out: &mut dyn alloy_rlp::BufMut) {
+        out.put_u8(self.tx_type() as u8);
+        self.rlp_encode(out);
+    }
+}
+
+impl Decodable2718 for TxDeposit {
+    fn typed_decode(ty: u8, data: &mut &[u8]) -> Eip2718Result<Self> {
+        let ty: OpTxType = ty.try_into().map_err(|_| Eip2718Error::UnexpectedType(ty))?;
+        if ty != OpTxType::Deposit as u8 {
+            return Err(Eip2718Error::UnexpectedType(ty as u8));
+        }
+        let tx = Self::decode(data)?;
+        Ok(tx)
+    }
+
+    fn fallback_decode(data: &mut &[u8]) -> Eip2718Result<Self> {
+        let tx = Self::decode(data)?;
+        Ok(tx)
+    }
+}
+
 impl Encodable for TxDeposit {
     fn encode(&self, out: &mut dyn BufMut) {
         Header { list: true, payload_length: self.rlp_encoded_fields_length() }.encode(out);
@@ -495,7 +522,7 @@ mod tests {
         tx_deposit.network_encode(&mut buffer_with_header);
 
         let mut buffer_without_header = BytesMut::new();
-        tx_deposit.eip2718_encode(&mut buffer_without_header);
+        tx_deposit.encode_2718(&mut buffer_without_header);
 
         assert!(buffer_with_header.len() > buffer_without_header.len());
     }

crates/consensus/src/transaction/envelope.rs

@@ -415,7 +415,7 @@ impl Encodable2718 for OpTxEnvelope {
                 tx.eip2718_encode(out);
             }
             Self::Deposit(tx) => {
-                tx.eip2718_encode(out);
+                tx.encode_2718(out);
             }
         }
     }

crates/protocol/src/deposits.rs

@@ -1,6 +1,7 @@
 //! Contains deposit transaction types and helper methods.
 
 use alloc::{string::String, vec::Vec};
+use alloy_eips::eip2718::Encodable2718;
 use alloy_primitives::{b256, keccak256, Address, Bytes, Log, TxKind, B256, U256, U64};
 use core::fmt::Display;
 use op_alloy_consensus::TxDeposit;
@@ -334,7 +335,7 @@ pub fn decode_deposit(block_hash: B256, index: usize, log: &Log) -> Result<Bytes
 
     // Re-encode the deposit transaction
     let mut buffer = Vec::with_capacity(deposit_tx.eip2718_encoded_length());
-    deposit_tx.eip2718_encode(&mut buffer);
+    deposit_tx.encode_2718(&mut buffer);
     Ok(Bytes::from(buffer))
 }